Optus, like other Australian mobile carriers, traps users into excessive charges by giving delayed billing information and refusing to show on your mobile "remaining uasage" in dollars and cents, that would allow the user to stay within the cap and the budget. Their roaming data GPRS and overseas call charges are truly exhorbitant, i.e. I paid 4000 times the fee for using Internet on my mobile I would have paid had I used a local Thai sim card (which I eventually did). Never use your Optus mobile overseas for any purpose unless you are a fool or a millionaire.

If you live in Australia, lobby for forcing the mobile carriers into disclosing "remaining credit" information on your mobile for every category. i.e. voice, data, sms, etc. See http://forums.whirlpool.net.au/forum-replies.cfm?t=1304836&p to give you tools for lobbying and complaints.

Many countries do force their mobile carriers to disclose "remaining credit" on the user's mobile at any time. Australia is truly behind in this. Millions of dollars have been ripped off by mobile carriers from ususpecting customers by unscrupulous carriers like Optus.